Stealth Aerial Vehicle

ABSTRACT

An aerial vehicle having a low radar signature includes a first side on which turbine openings, and payload bays or landing gear bays are disposed. A second side of the aerial vehicle is designed to have a smaller radar signature than the first side.

FIELD OF THE INVENTION

The invention relates to an aerial vehicle, in particular, a stealthaircraft, and to a method of operating an aerial vehicle.

BACKGROUND OF THE INVENTION

Aircraft and other aerial vehicles are frequently monitored by radarequipment. Aerial vehicles having a low radar signature have beendeveloped to evade this monitoring, i.e., aerial vehicles that, forexample, radiate back radar waves only at a low level in the directionof the radar equipment.

A low radar signature, which is the equivalent of a low probability ofthe aerial vehicle's being detected by radar, can be implemented or atleast enhanced, for example, by energy-absorbing paints,energy-diverting seals for the outer-skin joints, fewer and largerhinged flaps for maintenance instead of many small ones, accommodatingloads within interior shafts instead of having exterior loads.

Ninety percent of the improvement, i.e., the reduction in the radarsignature of an aerial vehicle, currently occurs by improving thegeometry of the aerial vehicle. This can be effected, for example, byreducing edge reflections whereby the edges are, for example,parallelized.

Examples of stealth aerial vehicles having an extremely low radarsignature include the strategic long-range bomber Northrop B-2, and theunmanned aircraft Boeing X-45 and Northrop X-47.

In aerial vehicles having an extremely low radar signature, anydisturbances in the aircraft surface can generate unwanted radarback-scattering. These disturbances can include, specifically, engineintakes and nozzles, as well as landing gear and weapons bay doors, thestealth concealment of which can entail a significant cost even when inthe closed state.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention are directed to an aerialvehicle, the stealth properties of which are especially difficult toovercome by radar beams.

A first aspect of the invention relates to an aerial vehicle. The aerialvehicle may, for example, be a manned aircraft or a UAV, i.e., anunmanned aerial vehicle.

In one embodiment of the invention, the aerial vehicle comprises atleast one turbine or at least one engine to propel the aerial vehicle.The turbine here has at least one turbine opening. For example, theturbine can comprise at least one air intake and at least one nozzleopening.

In addition, the aerial vehicle comprises at least one bay or aplurality of bays. Additional components of the aerial vehicle can beaccommodated by the bay(s) inside the aerial vehicle. These componentscan include a landing gear, payload, weapon, or releasable missile, suchas, for example, a bomb. A bay can be understood here to refer to a(closable) opening in the aerial vehicle that can be closed, forexample, by a hinged flap or a door. A bay can in other words be closedby a hinged flap. Bays of this type can include a landing gear bay, apayload bay, or a weapons bay.

In one embodiment of the invention, the aerial vehicle is designed tohave a low radar signature. Radar signature is understood here to referto the property of the aerial vehicle whereby incident radar waves fromone direction are reflected in the same direction. The radar signaturecan also be described as the radar cross-section (RCS). A small radarcross-section here means poor detectability by radar waves.

When the following and previous discussion refer to stealth propertiesor a stealth surface or stealth side, this is understood to refer to thefact that the relevant surface has a low radar signature. As has alreadybeen explained above, a low radar signature can be achieved by thegeometry of the aerial vehicle and by a radar-absorbing material, suchas a paint, applied to the surface. In other words, the aerial vehiclecan be stealth aerial vehicle in terms of radar waves.

In one embodiment of the invention, the at least one turbine opening andthe at least one bay are disposed on a first side of the aerial vehicle,while a second side of the aerial vehicle is designed to have a lowerradar signature than the first side. For example, all of the openingsand bays can be located on the first side, while the second side can befree of openings and bays. This enables the second side to have optimalstealth properties.

Based on the premise that the aerial vehicle generally turns the second(high-stealth) side towards a threat, it is not necessary for the firstside to have exactly the same degree of stealth. This allows highstealth properties to be dispensed with for the openings and the bays.

Positioning the sources of disturbance, such as openings and bays, onthe side opposite the threat achieves the result that these sources ofdisturbance are no longer directly exposed to the radar waves from thedirection of the threat, and therefore no longer have to undergo costlystealth treatment. In other words, all or many of the openingsdetrimental to RCS can be positioned on one side of the aerial vehiclein order to further minimize a radar signature in aerial vehicles havingan extremely low signature.

Configurational optimization of disturbance sources, i.e., openings andbays, of the aerial vehicle thus enables its radar signature to beoptimized in a specific direction.

In one embodiment of the invention, the second side has an essentiallyundisturbed or smooth surface. In particular, the second side can bedesigned without indentations, protrusions, and edges. This approachenables a “clean”, especially high-stealth (second) side to be createdwithout any disturbances in the surface. This can be achieved in termsof configuration by positioning cavities, such as intakes, nozzles,landing gear bays, and/or weapons bays, on the opposite (first) side—inparticular, those cavities that are open or are to be opened in flight.Based on the freely selectable attitude in flight, the aerial vehiclecan thus always orient the clean second side towards the radar threat(for example, ground-based radar) and thereby optimize the stealthproperties. The cost of minimizing radar backscatter due to secondaryscattering centers, such as, for example, openings and bays, can thus bereduced by disposing these scattering centers on the first side of theaerial vehicle.

In one embodiment of the invention, the second side does not have anybays. If, for example, the landing gear bays and payload or weapons baysare disposed on the same (first) side as the engine openings, the secondside is then relatively free of larger openings and can thus be providedespecially easily with stealth properties.

In one embodiment of the invention, the first side includes all of thebays and openings. This makes it possible for the first side not to haveany openings that would have to be given stealth properties.

In one embodiment of the invention, a bay is a landing gear bay or apayload bay. For example, all of the landing gear bays can be placed onthe first side on which the engine openings are also located. Thepayload and weapons bays can also be located on the first side. Inparticular, the landing gear bays, payload bays, and/or weapons bays canbe placed on the top side of the aerial vehicle. This may mean that theaerial vehicle has to turn over in order to release the payload, use theweapon, land, or take off.

In one embodiment of the invention, the first side is a top side of theaerial vehicle and/or the second side is a bottom side of the aerialvehicle. The aerial vehicle can, for example, be a flat flying body thatextends significantly further in the longitudinal and transverse axesthan in a vertical axis. In this case, the first and the second side canbe respectively the top and the bottom side of the aerial vehicle. Thetop or the bottom side of the aerial vehicle here can be characterizedby the orientation of the pilot or by technical limitations, such as,for example, the preferred attitude. If the first side is the top side,the pilot can, for example, fly in the upright position with the stealthsecond side facing down.

In one embodiment of the invention, the aerial vehicle is designedpreferably to fly in an attitude in which the second side is oriented inthe main threat direction. The main threat direction can be determined,for example, by a radar unit on the ground; thus points towards theground. For example, the aerodynamic shape of the aerial vehicle can bedesigned to have the greatest lift in the preferred attitude.

In one embodiment of the invention, only the second side of the aerialvehicle can be detected from one viewing direction. In other words, fromone viewing direction the second side completely hides the first side ofthe aerial vehicle.

As a result, a radar unit that beams radar waves in the viewingdirection of the aerial vehicle could only detect the second side. Sincethe second side has especially effective stealth properties, the aerialvehicle is able to remain invisible to the radar unit despite the factthat it is clearly possible that the radar unit would be capable ofdetecting the first side.

In particular, the first and the second sides can be situated oppositeeach other. It is also possible for only the first side to be detectedfrom another viewing direction.

In one embodiment of the invention, the aerial vehicle includes acockpit. The aerial vehicle can thus be a manned aerial vehicle. Thecockpit can be disposed on the first side. A cockpit, and especially thedome of the cockpit, can generate unwanted radar signatures. In thiscase, it may be possible for the pilot to be upside-down in the aerialvehicle during landing, takeoff, and when using the payload or weaponsbays.

In one embodiment of the invention, the aerial vehicle is designed forunmanned operation. The aerial vehicle requires for this purpose anonboard computer that is capable of flying the aerial vehicleindependently. The configurations of openings and bays described bothabove and below may be of interest specifically for unmanned aerialvehicles since the physiognomy of the pilot then does not have to betaken into account.

In one embodiment of the invention, the aerial vehicle is designed as aflying wing. A flying wing here can be an aerial vehicle that has afuselage and wing body. In other words, in a flying wing the wingscannot be distinguished visually from the fuselage. A flying wingconfiguration, which can be provided very effectively with stealthproperties, and has a first and a second side such as described bothabove and below, can be deployed, for example, against enemy air defensemeans.

Another aspect of the invention relates to a method of operating anaerial vehicle, in particular, an aerial vehicle such as that describedabove and below.

In one embodiment of the invention, the method comprises the steps:flying in an attitude in which a second side of the aerial vehicle facesin the direction of a threat, for example, downward, while the secondside is opposite a first side of the aerial vehicle on which nozzleopenings and a payload bay of the aerial vehicle are placed; switchingto an attitude in which the first side faces the direction of thethreat; releasing a payload from the payload bay. The payload bay can beopened before releasing the payload. After releasing the payload, thepayload bay can be closed again.

Following this, the aerial vehicle can switch back to the attitude inwhich the second side faces the direction of the threat. This approachenables the radar signature of the aerial vehicle to be very low in thedirection of the threat during the majority of the time of flight. Onlywhen releasing the payload does the aerial vehicle turn its first side,the side with weaker stealth properties that the second side, towardsthe threat.

In one embodiment of the invention, the method comprises the steps:taking off in the attitude in which the first side faces down;retracting a landing gear into a landing gear bay that is placed on thefirst side; switching to the attitude in which the second side faces thedirection of the threat; switching to an attitude in which the firstside faces down; extending the landing gear; landing in the attitude inwhich the first side faces down. In other words, the aerial vehicle canbe designed to land and take off on its back. In order to land and takeoff, the aerial vehicle can in other words rotate into a position inwhich the side with the landing gear points down (i.e., towards theground). Strong stealth properties are generally not required duringtakeoff and landing.

The following discussion describes exemplary embodiments of theinvention in detail with reference to the attached figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of the first side of an aerial vehicle basedon one embodiment of the invention.

FIG. 2 is a schematic view of the narrow side of the aerial vehicle inFIG. 1.

FIG. 3 is a schematic view from the front of the aerial vehicle in FIG.1.

FIG. 4 is a schematic view of the first side of the aerial vehicle inFIG. 1 as seen obliquely from above.

FIG. 5 is a schematic view of the aerial vehicle in FIG. 1 whenoperating on the ground.

FIG. 6 is a schematic view of the aerial vehicle in FIG. 1 duringtakeoff.

FIG. 7 is a schematic view of the aerial vehicle in FIG. 1 when in thecruise flight attitude.

FIG. 8 is a schematic view of the aerial vehicle in FIG. 1 with payloadbay open.

The reference numerals used in the figures and their meanings areprovided in summary form in the list of reference numerals.

As a rule, identical or similar components are provided with identicalreference numerals.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIGS. 1 through 4 depict aerial vehicle 10 from different directions.FIG. 1 provides a view of the first side 12; FIG. 2 provides a view ofthe narrow side; FIG. 3 provides a view from the front; while FIG. 4provides a view of first side 12 as seen obliquely from above.

Aerial vehicle 10 is a flying-wing aircraft having an essentiallytrapezoidal fuselage. On first side 12, a nozzle opening 14 is locatedat the back end, while two intakes 16 are located at the front end thatare disposed symmetrically relative to a center axis of aerial vehicle10. A turbine 18 is located in aerial vehicle 10 in order to propel it,which turbine can draw in air through intakes 16, compress it, and ejectit through nozzle openings 14. Intakes 16 and nozzle openings 14 areturbine openings of aerial vehicle 10.

A payload bay 20 is located on first side 12, which bay is closed by twohinged flaps or doors 22. The payload bay is disposed symmetricallyrelative to the center axis, and between intakes 16 and nozzle opening14. Two main landing gear bays 24 are disposed relative to the centeraxis adjacent to payload bay 20, while a nose landing gear bay 26 isdisposed ahead of payload bay 20 between both intakes 16. Landing gearbays 24 and 26 are closed by hinged flaps or doors 28.

FIGS. 2 and 3 also reveal a second side 30 of aerial vehicle 10 that isopposite first side 12. The entire surface of the aerial vehicle isformed by the two sides 12 and 14. Turbine openings 14, 16, and bays 20,24, 26, and thus all of the openings here, are disposed on first side12.

No turbine openings or bays are located on second side 30. Second side30, in particular, has no openings but rather a completely undisturbed,smooth surface that exhibits a very low radar signature. The low radarsignature of second side 30 that is determined the side's geometry canbe reduced even further by means of an appropriate coating. Inparticular, it can be significantly smaller than the radar signature offirst side 12. As is evident in FIG. 3, second side 30 has a surfacethat is slightly curved towards the center.

The figures depict unmanned aerial vehicle 10 that is designed as aflying wing. However, it is also possible for a similar manned aerialvehicle to have this type of configuration of turbine openings 14, 16,and bays 20, 24, 26. In this case, a cockpit 32, for example, could bedisposed on first side 12.

FIGS. 1 through 4 and FIG. 7 depict the aerial vehicle in a cruiseflight attitude in which side 12 faces up while second side 30 facesdown. In a manned aerial vehicle, the top side and the bottom side ofthe aerial vehicle can be defined by the orientation of the pilot. As aresult, first side 12 can be a top side of aerial vehicle aerial vehicle10 while second side 30 can be a bottom side of aerial vehicle 10.

FIGS. 5 through 7 illustrate the operation of aerial vehicle 10.

FIG. 5 depicts aerial vehicle 10 on the ground. Landing gear hingedflaps 28 have been opened and landing gear 34 extended. First side 12faces down. Second side 30 faces up.

FIG. 6 depicts aerial vehicle 10 during takeoff. First side 12 alsofaces down during takeoff. After takeoff, landing gear 34 is retractedinto landing gear bays 24, 26, and aerial vehicle 10 switches to anattitude in which second side 30 faces in the direction of a threat.

A threat of this type is depicted in FIG. 4 in the form of a radar unit36. Since radar unit 36 is located on the ground while aerial vehicle 10is the air, the threat comes from below and second side 30 faces down.

Only second side 30 of aerial vehicle 10 is visible from the viewingdirection of radar unit 36. Radar waves 38 that are emitted by radarunit 36 in the direction of the aerial vehicle impinge only on second,high-level-stealth side 30 and are either absorbed by this side orscattered away from radar unit 36.

Aerial vehicle 10 switches to an attitude, such as that depicted in FIG.8, in order, for example, to drop or fire a weapon at threat 36. Firstside 12 points towards threat 36 in this attitude. In this attitude,payload bay 20 can be opened and the payload, in the form of a bomb orrocket, can be released. Payload bay 20 is then closed. To be sure,aerial vehicle 10 can be detected more readily when in this attitude.However, it only has to remain in this attitude for a short time.

After using payload bay 20, aerial vehicle 10 switches back into anattitude, such as that depicted in FIG. 7. After returning home, aerialvehicle 10 switches again into the attitude depicted in FIG. 6, extendsthe landing gear, and lands.

It must be added that “comprising” does not exclude any other elementsor steps, while “a/an” or “one” do not exclude a plurality. It mustfurthermore be stated that the features or steps that have beendescribed with reference to one of the above exemplary embodiments canalso be applied in combination with other features or steps of otherexemplary embodiments described above. Reference numerals in the claimsmust not be viewed as constituting a restriction.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Since modifications of thedisclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

LIST OF REFERENCE NUMERALS

-   10 aerial vehicle-   12 first side-   14 nozzle opening-   16 air intake-   18 turbine-   20 payload bay-   22 hinged flap-   24 main landing gear bay-   16 nose landing gear bay-   28 hinged flap-   30 second side-   32 cockpit-   34 landing gear-   36 radar unit-   38 radar waves

1-15. (canceled)
 16. A method of operating an aerial vehicle, the methodcomprising the acts of: taking off the aerial vehicle in a secondattitude in which a first side faces down, wherein the first side of theaerial vehicle has a landing gear bay, and wherein a second side of theaerial vehicle has no bays, has a smaller radar signature than the firstside and is arranged opposite to the first side of the aerial vehicle;retracting a landing gear into the landing gear bay that is arranged onthe first side; switching from the second attitude to a first attitudein which the second side faces in a direction of a threat during aportion of flight of the aerial vehicle; switching from the firstattitude to the second attitude in which the first side faces down;extending the landing gear while the aerial vehicle is in the secondattitude; and landing the aerial vehicle in the second attitude in whichthe first side faces down.
 17. The method according to claim 16, whereinthe second side has an essentially undisturbed surface.
 18. The methodaccording to claim 16, wherein the first side includes all bays andopenings of the aerial vehicle.
 19. The method according to claim 16,further comprising configuring the landing gear bay to be closable by ahinged flap.
 20. The method according to claim 16, wherein the firstside is a top side of the aerial vehicle and the second side is a bottomside of the aerial vehicle.
 21. The method according to claim 16,further comprising: disposing at least one payload bay on the first sideof the aerial vehicle.
 22. The method according to claim 16, whereinfrom one viewing direction only the second side of the aerial vehiclecan be detected.
 23. The method according to claim 16, furthercomprising: disposing a cockpit on the first side.
 24. The methodaccording to claim 16, further comprising: configuring the aerialvehicle for unmanned operation.
 25. The method according to claim 16,further comprising: configuring the aerial vehicle as a flying wing.